By CAROLINE KNAPP

mong dog people, the name Elizabeth Marshall Thomas is a bit of a Rorschach test, with associations all over the map. To some dog owners, she's a genius, a guru, a woman with the keys to the canine city. So many of us want to know what really goes on in those baffling, beloved dog brains -- what motivates dogs, how they think and feel -- and Thomas's 1993 best seller, ''The Hidden Life of Dogs,'' seemed to deliver the goods: here was a woman, an anthropologist no less, who lived with 11 dogs, observed them daily, actually followed them around on a bicycle to see what they did when left to their own devices. But if the result -- an insider's look at the politics of hierarchy and territoriality that so define canine life -- gratified some, it infuriated others. Scientists -- particularly those who don't believe that animals are capable of feeling in the first place -- condemned the book as an exercise in anthropomorphic pseudoscience. Spying on dogs? On a bicycle? Please. And to a third camp, the whole thing smacked of irresponsibility: 11 dogs, the males unneutered, all of them allowed to run loose in the city -- this sounded less like an anthropological field study than a recipe for chaos.

Thomas's sequel, ''The Social Lives of Dogs,'' picks up where its predecessor left off -- it describes life amid the pack she acquired after her original 11 began to die off -- and while critics from the hard sciences will still bristle at her sense of dog psychology, the rest of us will be delighted, some because Thomas brings the same degree of observational precision to this project and some for a more pragmatic reason: the author has moved her show to rural New Hampshire, where the dogs are safer.

The new pack begins with Sundog, a large white stray Thomas discovered during a visit to the city; over time, the pack swells to include five humans, seven dogs, nine cats and five parrots. This ''churning caldron of a household'' becomes Thomas's live-in laboratory, a place of extraordinary ordinariness: nothing very remarkable happens unless you believe, with the author, that everything dogs do is remarkable, and then life among them becomes endlessly fascinating. How do different dogs react when you place a biscuit under a cloth, thus presenting a problem to solve? How does an underconfident dog learn to negotiate stairs? How do country dogs react when taken on a trip to Manhattan? (Answer: unable to see trees or sky or dirt, they seem to think it's a giant building, which causes considerable distress on the bladder front; being good dogs, they refuse to relieve themselves indoors.)

These are the kinds of quirky details Thomas explored the first time around, and she's masterly at description, equipped with a deep regard for the essential dogness of dogs and attuned to the tiny things -- a wag here, an expression there -- that capture who they are. But her take is more expansive here: this is a quieter, gentler Thomas, less of a dispassionate observer and more of an engaged participant in her dogs' lives, and the result is a fuller, more affecting read.

What do dogs want? In ''The Hidden Life,'' Thomas answered this question unequivocally: ''They want each other. Human beings are merely a cynomorphic substitute.'' This may have been true of that pack -- Thomas maintained a distance from those dogs that felt both geographic and emotional, as though their relationship to the human world (and her relationship to them) were secondary, if not beside the point. In this work, her greater emotional proximity to the dogs puts her on more richly textured territory, a place where field observation meets feeling.

She is still fascinated by dogs' relationships with one another, and, as in ''The Hidden Life,'' she vividly brings to life the dynamics of hierarchy and social longing that characterize them. We see how the confident, capable Sundog so easily maintains his status as the alpha male, and why Misty, a Belgian sheepdog who spent her puppyhood alone in a crate, remains so insecure about her position as Dog 2. We get carefully rendered glimpses of the affection that crops up inexplicably between some dogs (in one of the book's sweeter passages, Sundog develops a fondness for an overweight beagle mix named Bean), and of the range of feeling -- indifference, begrudging acceptance, competitiveness -- that exists between others. We see dogs as dogs, with their own rules and codes of conduct.

But Thomas is equally attentive to the dog-human bonds that form within her household, and even the dog-cat and dog-cat-human bonds, and so we see dogs forming special alliances with particular people, and cats splitting off to join this subpack or that one; we see cats lying with dogs on their beds, wrapping their bodies around the dog's head as a cat might cradle a kitten; we see how aware each species is of the other, and how many subtle accommodations the members must make in order to coexist. The reach in this book is larger, creating a sense of the deep and daily connection between human and dog -- the mutuality of affection and need, the mysterious and pure sympathy that transcends language, the anguish of loss.

Thomas is still a controversial, eccentric character, and the book is not without its controversial, eccentric features. An epilogue on cross-species telepathy feels a bit strained; an appendix on keeping parrots feels like an unnecessary afterthought. The author also leaves herself open to some of the same criticism that followed ''The Hidden Life'': readers wary of anthropomorphism will groan when she speculates about whether Sundog, while masturbating, is engaged in a sexual fantasy; dog owners horrified by her laissez-faire approach to training may find her appendix on the control of dogs heavy-handed (in it, she rails against the ''iron hand of dog fascism'' that she believes pervades American pet ownership). But Thomas has cracked open the door she first unlocked in ''The Hidden Life'' by several degrees, and it's worth peering past the barriers (too little science for some, too much dogma for others) to see what's inside. There's plenty of heart in this caldron. And, of course, lots of dogs.

Caroline Knapp is the author of ''Pack of Two: The Intricate Bond Between People and Dogs.''